The present invention relates to an automatic temperature control circuit for use in after-harvest-management of wet-stored grains. More specifically, it monitors energy exchanges which occur between living seeds and their environment as they go through their natural cycle of curing.
As taught in U.S. Pat. Nos. 3,408,747; 4,045,878; and 4,053,991, optimum moistures in grain vary with grain temperatures. In U.S. Pat. No. 4,045,878 it is taught that these conditions of moisture contribute to the curing process, which includes biochemical restructuring of the seed as it goes through its ripening process. Environmental conditions of temperature/humidity interact with the seeds to influence these processes; and in a closed storage environment, adverse conditions will rapidly develop unless indicators and controls are used to monitor conditions and to permit activation of air controlling means (humidity and volume) to remove the adverse conditions.
In U.S. Pat. No. 3,408,747, a method and arrangement of structures are taught which permit management responses according to conditions of grain volume, air volume and temperatures during the ventilation and drying of grain so as to minimize adverse biochemical changes in the seed, and which, in conjunction with a grain moisture chart, make possible the indication of grain moisture by comparing the in-going air temperature (dry-bulb) against the out-going air temperature (wet-bulb).
This same patent teaches a temperature ceiling under which heat additions should be kept when used in drying grain, and specifies the criticalness of air temperature and air volume for optimum conditioning of grain.
Because of the stabilizing effect of cooling, significant reductions in ventilation are permissible. In other patents cited, "unheat curing" or removal of "free heat" from atmospheric air so as to reduce the seed temperatures to lowest possible levels given atmospheric conditions is taught. In grain, least deterioration occurs at lowest temperatures; which is to say that optimum quality in grain is achieved when grain is reduced to a least energy state by using atmospheric air to reduce the energy state (temperature) of grain when its temperature is higher than the atmospheric air, and on a continuing basis to be able to monitor and control moisture removal from the grain environment by monitoring heat-loss during ventilation.
"Curing" of grain is new art in the field of managing grain and is not to be confused with "drying". Drying is simply removal of water from grain in structures which use arbitrary levels of heat and air as determined by the mechanical engineering design of the structure. "Curing", on the contrary, relates to a process which includes optimizing biochemical changes in the product being cured. Because grain releases moisture to the surrounding air as it cures, drying of the product also occurs. The instant teaching is one that avoids heat applications which removes moisture from grain at a rate faster than occurs in the atmospheric environment.
This invention relates to a monitor and control which senses energy-exchanges (heat) as they occur between living seed and the atmosphere, and which controls the activation of air controlling means, e.g., infrared emitters and/or fans in response to evaporative cooling.
Energy radiation from the sun charges atmosphereic air with energy. Varying amounts of "free heat" are available in atmospheric air and are measurable in evaporative cooling. The "mean wet-bulb temperature" indicates the "free heat" available to grain in open air curing.
U.S. Pat. Nos. 3,408,747 and 4,045,878 identify a "dormancy index" or equilibrium moisture and temperature in grain in response to average, atmospheric conditions.
This invention allows selective control of activation of dehumidifiers when the wet-bulb depression is less than the mean, wet-bulb depression in the geographical area applicable, and deactivation of dehumidifying apparatus when evaporative cooling exceeds the mean, wet-bulb depression.
U.S. Pat. No. 3,408,747 teaches a static psychrometer including structure (perforated floor) for allowing air to escape from the air plenum; a wetted member (grain) exposed to the escaping air; temperature sensors giving the temperature of the air before being exposed to the wetted member and again after being exposed to the wetted member, and a pre-composed grain moisture chart identifying equilibrium-grain-moisture to the two temperature readings obtained.
The instant invention describes a solid state structure capable of continually displaying at ground level on a digital display the in-going air temperature and the out-going temperature of the differential therebetween, and a solid state structure which activates and deactivates air modifying means in response to the differential temperature regardless of fluctuations in atmospheric air temperature.
In U.S. Pat. No. 3,408,747 the criticalness of air volume and air temperature is noted as well as their interaction with grain of varying moisture contents. These critical relationships must be maintained if seed-life is to be preserved. Because of changes resulting from interactions, i.e., adding of grain and/or colder temperatures, some means for constantly monitoring air quantity (volume) and air quality (temperature) is essential. The monitoring device employed for measuring air volume is a conventional manometer mounted on the plenum wall, used with fans of known air deliveries at specific pressures (inches displacement of water). By maintaining a consistent relationship of fan horsepower to bushels of grain, e.g., 1 horsepower per 1,000 bushels of grain, and by keeping grain depths the same in all situations, i.e., never exceeding 14', the volume of air to the grain will basically be the same in all structures at a given depth, and the pressure will essentially be the same. Maximum pressure is observed in the plenum into which air is being introduced. The pressure in the grain column decreases the further the distance from the plenum, so that least pressure is in the exhaust plenum, which may or may not be atmospheric air pressure.
For optimum use of air, it is desirable to bring it to a maximum level of moisture carrying capacity consistent with a moisture level not hazardous to the grain. Thus, it is useful to be able to monitor the humidity condition of air and to increase the ventilation rate and/or increase the moisture-holding capacity of air when the humidity is too high.